Grinding apparatus

ABSTRACT

A grinding apparatus having a pair of grinding discs, at least one of which discs being rotatable and at least one of the discs being adjustable with respect to the other disc by means of two concentric interengaging screws, the outer screw surrounding the inner screw also engaging a part of the casing carrying the adjustable disc.

United States Patent 1191 1111 3,827,644 Johansson [4 Aug. 6, 1974 [5 1GRINDING APPARATUS 1,116,611 11/1914 Nash 241/286 x 1,123,494 1/1915 C241/259.3 [75] Invent: Johan Inge khansson, 1,135,313 4/1915 1121?, eta1. 241/247 Taby, Sweden 2,743,874 5/1956 Asplynd 241/259.1 x 3,371,8733/1968 Thomas 241/259.1 X [73] Ass'gnee' 2:23;? Akt'ebolagstockholm3,625,441 12/1971 54111616111 ..241/259.1x

[22] Filed: July 1, 1971 P E G n Y C J rimary xaminer ranv1 e uster, r.[21] Appl' l59069 Assistant Examiner-Howard N. Goldberg RelatedApplication Data [63] Continuation of Ser. No. 6,112, Jan. 27, 1970,

abandoned. ABSTRACT [30] Forelgn Apphcamn pnomy Data A grindingapparatus having a pair of grinding discs, at Feb. 19, 1969 Sweden2311/69 least one of which discs being rotatable and at least one of thediscs being adjustable with respect to the [52] US. 81. 24l/259.3, 2332087501; other disc by means of two concentric interengaging Ill. CScrews, the outer Screw Surrounding the inner screw 58 Fleld of Search241/247, 259.1, 253.3, also engaging a part of the casing carrying theadjust 86 able disc.

[56] References Cited UNITED STATES PATENTS 21 Clauns, 3 Drawing Flgures 932,882 8/1909 Moore et a1. 241/247 PAIENIEDAUB 61 M .3 27 s44sum 'uFz Figl 28 'INVEWBE GRINDING APPARATUS This is a continuation ofSer. No. 6,1 12, filed Jan. 27, 1970, and now abandoned. I

This invention relates to a grinding apparatus with grinding discshoused in a casing of which discs at least one is rotatable and whichdiscs between themselves form a grinding space for the grinding produceconsisting of vegetable or similar material.

More specifically, the invention relates to grinding apparatus of thekind in consideration wherein at least the one grinding disc is formedwith two concentrical annular elements. The grinding discs are made sothat a gradual disintegration, usuallydenoted as, respectively,defibration and refining of the produce passing through the grindingspace is effected. According to the US. Pat. No. 3,684,200 the inner oftwo concentric annular of disc elements is axially adjustable relativelyto the outer one for compensation of the non-uniform wear of thegrinding surfaces of the elements. The wear is namely greatest in theinner or primary grinding zone which receives the coarser grindingproduce, whereas this latter when entering the outer, secondary grindingzone has already been subjected to a homogenization and a pre-working. I

One main object of the invention is to provide an arrangement whichpermits adjustment of one grinding discor a portion thereof such as theinner one of two concentric annular elements by actuation from outsidewhile the grinding apparatus is in operation and thus the grinding discsare subjected to the high pressure acting on the grinding produce. Thispressure may be createdhydraulically, i.e. in the manner disclosed inthe US. Pat. No. 2,891,733. The arrangement shall according to theinvention be capable of permitting fine adjustment of the disc or theannular element in axial direction with very high exactness, such ashundredths of one millimeter to attain the most favourable quality ofthe grinding produce or the highest possible capacity of the grindingapparatus in response to the properties of the grinding produce.

Another object of the invention is to provide an arrangement which iscapable of compensating during the operation proper, i.e. anyinterruption of the operation, for the unavoidable wear on the grindingdisc or the annular element, respectively.

According to one main feature of the invention the grinding disc or asuitably radially inner annular element is adjustable by means of twoscrews disposed concentrically relatively one another and having threadscooperating with one another, that in addition the outer screw and apart carrying said grinding disc or said annular element have threadscooperating with one another, that the two pairs of threads are threadedin the same direction but with different pitches and that one of thescrews is rotationally stationary.

In accordance with the invention the threads due to their great pitchcan be made so strong that they are capable of withstanding without anydisturbing deformation the high axial pressure exerted on the grindingdiscs, which may amount to many tons per pair of screws. At the sametime, the resulting axial displacement of the grinding disc or theannular element becomes little for one part-tum through an angle of therotatable screw, whereby an exact fine adjustment of the grinding discor the annular element is rendered possible. According to a particularlyadvantageous embodiment of the invention a closed space which isconnectable to a pressure source for a pressure fluid is provided behindthe adjustable grinding disc or annular element. Hereby, the threads canbe relieved to a substantial degree from the high axial working pressureduring the adjustment operation proper.

Further objects and advantages of the invention will become apparentfrom the following description, considered in connection with theaccompanying drawings, which form part of this specification and ofwhich:

FIG. 1 is a longitudinal sectional view of a portion of a grindingapparatus constructed according to one embodiment of the invention.

FIG. 2 shows two screws and adjacent parts in the same section as inFIG. 1 but in a greater scale.

FIG. 3 is an end view of the casing of the grinding apparatus shown inFIG. 1.

Referring to the drawings, reference numeral 10 denotes the rigid standof the apparatus which forms a casing which is passed by a rotatableshaft 12 extending from end to end. The shaft 12 carries a grinding disc14 to which a number of concentrically disposed annular or discelements, in the present case three elements denoted 16, 18, 22 areconnected by means of bolts not shown. Most suitably each of the annularelements 16, 18, 22 is composed of segments. Provided in the centre ofthe grinding disc 14 is a disc member 20 which has for its purpose tofeed the grinding produce introduced by means of a screw conveyor 24,and being e.g. in the form of chips or fibre pulp, in a radially outwarddirection. A stationary grinding disc is composed of two concentricstator rings 28, 30 supporting grinding disc elements 32 and 34, 36,respectively, each of which also may be composed of segments and betweenwhich and the rotatable disc elements 16, 18, 22 a grinding space isformed, which is passed by the grinding produce at an outward direction.The segments of the grinding discs are in known manner formed with ribsand grooves.

The outer stator ring 28 is rigidly secured within the stand 10, whereasthe inner stator ring 30 is axially adjustable by means of pairs ofscrews formed according to the invention. Each of these pairs comprisesan outer hollow screw 38, which at its external surface is formed withthreads 40 cooperating with the threads 42 formed on an inner flangewithin a sleeve 44 which is rigidly anchored in an axial recess in thecasing or stand 10. An inner screw 48 is formed with an external thread50 which cooperates with an internal thread 52 formed in the outer screw38. The screw 48 extends through the sleeve 44 and bears on the statorring 30. A lock pin 54 is disposed freely movable within the inner screw48 and its end portion is inserted by screwing it into the stator ring30. By driving home this lock pin at the outer end thereof the twoscrews are fixed in predetermined positions relative one another and thestand, respectively. The sleeve 44 is at its interior end bent inwardlytowards the screw 48 and forms a guide surface 56 for said screw, whichguide surface may house a sealing ring 58.

The threads 40, 42 between the outer retainer screw 38 and thestationary sleeve 44 are preferably rightthreaded and have a relativelygreat pitch, such as 3 mms per turn. The threads 50, 52 between the twoscrews 38, 48 are threaded in the same direction, i.e. in the presentcase also right-threaded, and they have a still greater pitch such as 4mms per turn. The outer screw 38 is at its outwardly facing end formedwith a gear ring 60, which cooperates with an inner gear ring 62 formedon an annular member 64 which is disposed around the circumference ofthe stand inside a space which widens to recesses 66 at the individualpairs of screws. The annular member 64 is externally mounted in abearing ring, such as a strip 65 of Teflon (R) or some other materialhaving a low friction coefficient. A number of pairs of screws 38, 48,such as six such pairs, are uniformly spaced about the circumference(see FIG. 3) and the outer screw of each pair is in gear connection withthe common annular member 64 which is turned by means of a gear 74. Thusthe stator ring 30 when being adjusted to its axial position will beactuated simultaneously by a plurality of screws 48, such as six screwsin the illustrated embodiment.

The inner screw 48 has a non-circular, such as hexagonal, outer endportion 68 which fits into a noncircular, such as l2-sided, apertureformed in a plate 72 rigidly attached to the stand 10. Thus the screw 48cannot be rotated but only be displaced axially.

Pressure oil from a pressure source not shown is supplied to the threadsof each pair of screws through a conduit 76, which opens into channels78, 80 formed in the sleeve 44 and the outer screw 38, respectively.Said screw 38 is also formed with an axial channel 82 for equalizationof the pressure in the closed chamber 84 within the sleeve 44, when thescrew 38 moves axially and thus changes the volume of said chamber. Thechamber 84 is sealed against the surrounding parts by means of sealingrings 86, 88 in addition to the sealing ring 58.

A pressure fluid such as a liquid, preferably water, is supplied from apressure source not shown through a pipe 90 to a space 92 located at therear side of the stator ring 30. The stator ring 30 is mounted on theouter stator ring 28 by means of a bearing ring 94 and inwardly on aflange 96 formed on the casing 10 by means of a bearing ring 98. Thesebearing rings may consist of strips of material having a low frictioncoefficient, such as Teflon (R) which render the axial displacement ofthe stator ring 30 more easy. A sealing ring 100 may be provided inaddition between the stator rings 28 and 30. By supplying pressure fluidto the space 92 an increased pressure is created therein which iscontrollable by means of a pressure controller 102 provided in adischarge outlet.

The device operates in the following manner. During operation of thegrinding apparatus the grinding produce such as the chips or the fibrepulp is introduced by the conveyor 24 into the space between the twogrinding discs within which it is carried radially outwardly, whilebeing disintegrated into fibers or fibriles, respectively. In thisoperation, the rotating grinding disc 14 is subjected to a strong axialpressure in a direction towards the stationary grinding disc, as willbecome evident from e.g. the patent specifications referred to above.The pressure acting on the inner stationary stator ring 30 may amount tomany tens of tons. According to the invention an axial adjustment of thestator ring or disc 30 can now be effected during operation in responseto the desired grinding conditions or for compensation of the wear onthe disc elements 34, 36 or 18, 22, respectively, by means of the pairsof screws 38, 48. These pairs of screws are actuated together by meansof the gear ring 64, whereby the screw 38 is turned and at the same timedisplaced axially over a distance for each annular part turn or rotationwhich corresponds to the pitch of the threads 40, 42. The inner screw 48is actuated also by said turning movement, but as it cannot rotate, itwill be displaced axially only. As the threads are directed in the samedirection, and the pitch of the one pair of threads, in the embodimentshown, the pitch of the threads 50, 52 is greater than that of thethreads 40, 42, the turning of the outer screws 38 will result in anaxial displacement of the inner screw 48 over a distance correspondingto the difference in the pitches of the threads. In this way a fine andcorrect adjustment of the stator ring 30 is rendered possible while atthe same time the threads which transfer the axial pressure from thestator disc 30 to the casing 10 may have high structural strength so asto eliminate any appreciable deformation. It may be pointed out that theadjustment of the grinding surfaces of the grinding discs relative oneanother must be effected with an exactness of a hundredth of lmillimeter, for which reason it is essential that non-controllabledeformation shall be avoided of those parts which transfer the axialpressure. The threads between the screws or between one of them at thestationary sleeve 44 are lubricated by means of pressure oil suppliedfrom the conduit 76.

In order to relieve the pairs of screws 38, 48 as much as possible fromthe high grinding pressure during the adjustment of the stator ring 30,it is advantageous to introduce pressure fluid through the conduit intothe space 92. Due to the relatively great surface of the stator disc 30,this pressure fluid need not exert any particularly high pressure toobtain compensation so that the threads during the adjustment operationare relieved entirely or at least to a major extent from the grindingpressure. Also during normal operation of the grinding apparatus a minoroverpressure should be maintained in the space 92 to avoid waterintermixed with fibres from leaking out from the grinding disc to thescrew 38, 48.

While one more or less specific embodiment of the invention has beenshown and described, it is to be understood that this is for purpose ofillustration only, and that the invention is not to be limited thereby,but its scope is to be determined by the appended claims.

What is claimed is:

l. A grinding apparatus with grinding discs housed in a casing of whichdiscs at least one is rotatable and which discs between themselves forma grinding space for the grinding produce consisting of vegetable orsimilar material, characterized in that one of the grinding discs isadjustable by means of two screws disposed concentrically relatively oneanother and having threads cooperating with one another, that inaddition the outer screw and a part carrying said grinding disc havethreads cooperating with one another, that the two pairs of threads arethreaded in the same direction but with different pitches and that oneof the screws is rotationally stationary.

2. The grinding apparatus as claimed in claim 1, characterized in that aplurality of concentrically disposed screws are distributed about thecircumference of the grinding disc and that the outer screw in each pairis adapted to be turned by a common actuating member.

3. The grinding apparatus of claim 2, characterized in that the commonactuating member is a geared ring.

4. The grinding apparatus as claimed in claim 1, characterized in thatsaid inner screw is devised loosely to bear against the grinding disc,but to be locked in relation to the grinding disc by means of a lockingmember located within the inner screw and actuatable from outside.

5. The grinding apparatus as claimed in claim 1, characterized in thatthe threads formed between the outer of the two concentrically disposedscrews and the stationary part have a smaller pitch than the threadsexisting between the screws.

6. The grinding apparatus as claimed in claim 1, characterized in thatthe two pairs of threads are rightthreaded.

7. The grinding apparatus as claimed in claim 2, characterized in thatthe outer screws in each pair of screws have a gearing ring whichcooperates with said geared ring and at the same time is actuated bysaid geared ring.

8. The grinding apparatus as claimed in claim 1, characterized in thatdisposed behind the adjustable grinding disc is a closed space which isconnectable to a pressure source for a pressure fluid.

9. The grinding apparatus as claimed in claim 8, characterized in thatarranged in a pressure fluid conduit connected to the space is apressure controller for determining the magnitude of the relievepressure acting on the grinding disc.

10. A grinding apparatus with grinding discs housed in a casing in whichdiscs at least one is rotatable and which discs between themselves forma grinding space for the grinding produce consisting of vegetable orsimilar material, at least one grinding disc being formed with twoconcentrical annular elements, characterized in that one of said annularelements is adjustable by means of two screws disposed concentricallyrelatively one another and having threads cooperating with one another,that in addition the outer screw and a part carrying said annularelement have threads cooperating with one another, that the two pairs ofthreads are threaded in the same direction but with different pitchesand that one of the screws is rotationally stationary.

11. The grinding apparatus as claimed in claim 10, characterized in thatthe adjustable annular element is the radially inner one.

12. The grinding apparatus as claimed in claim 10, characterized in thata plurality of concentrically disposed screws are distributed about thecircumference of the annular element and that the outer screw in eachpair is adapted to be turned by a common actuating member.

13. The grinding apparatus as claimed in claim 12, characterized in thatthe common actuating member is a geared ring.

ing member located within the inner screw and actuatable from outside.

15. The grinding apparatus as claimed in claim 1, characterized in thatthe threads formed between the outer of the two concentrically disposedscrews and the stationary part have a minor pitch than the threadsexisting between the screws.

16. The grinding apparatus as claimed in claim 1, characterized in thatthe two pairs of threads are rightthreaded.

17. The grinding apparatus as claimed in claim 12, characterized in thatthe outer screws in each pair of screws have a gearing ring whichcooperates with said geared ring and at the same time is actuated bysaid geared ring.

l8.-The grinding apparatus as claimed in claim 1, characterized in thatdisposed behind the adjustable annular element is a closed space whichis connectable to a pressure source for a pressure fluid.

19. The grinding apparatus as claimed in claim 18, characterized in thatarranged in a pressure fluid conduit connected to the space is apressure controller for determining the magnitude of the relievepressure acting on the annular element.

20. A grinding apparatus having a pair of grinding discs forming betweenthem a grinding space for the material to be ground of which discs atleast one is rotatable, and at least one of which discs is provided withtwo concentrical annular elements, characterized in that one of saidannular elements is adjustable by screw means including interengagingthreads, a closed space being disposed behind said adjustable annularelement, said space being connectable to a pressure source for apressure fluid, so as to relieve said threads from the grinding pressurebetween the grinding discs during the adjustment of the annularelements.

21. A grinding apparatus having a pair of grinding discs forming betweenthem a grinding space for the material to be ground of which discs atleast one is rotatable, and at least one of which discs is provided withtwo concentrical annular elements, characterized in that one of saidannular elements is adustable by means including two concentricalinterengaging screws, the outer surrounding screw also having threadsengaging a screw threaded part of the casing carrying said annularelement, and a closed space behind said annular element which is adaptedto be connected to a source for supplying fluid under pressure wherebyto release said threads from the grinding pressure between the grindingdiscs during adjustment of the annular element.

1. A grinding apparatus with grinding discs housed in a casing of whichdiscs at least one is rotatable and which discs between themselves forma grinding space for the grinding produce consisting of vegetable orsimilar material, characterized in that one of the grinding discs isadjustable by means of two screws disposed concentrically relatively oneanother and having threads cooperating with one another, that inaddition the outer screw and a part carrying said grinding disc havethreads cooperating with one another, that the two pairs of threads arethreaded in the same direction but with different pitches and that oneof the screws is rotationally stationary.
 2. The grinding apparatus asclaimed in claim 1, characterized in that a plurality of concentricallydisposed screws are distributed about the circumference of the grindingdisc and that the outer screw in each pair is adapted to be turned by acommon actuating member.
 3. The grinding apparatus of claim 2,characterized in that the common actuating member is a geared ring. 4.The grinding apparatus as claimed in claim 1, characterized in that saidinner screw is devised loosely to bear against the grinding disc, but tobe locked in relation to the grinding disc by means of a locking memberlocated within the inner screw and actuatable from outside.
 5. Thegrinding apparatus as claimed in claim 1, characterized in that thethreads formed between the outer of the two concentrically disposedscrews and the stationary part have a smaller pitch than the threadsexisting between the screws.
 6. The grinding apparatus as claimed inclaim 1, characterized in that the two pairs of threads areright-threaded.
 7. The grinding apparatus as claimed in claim 2,characterized in that the outer screws in each pair of screws have agearing ring which cooperates with said geared ring and at the same timeis actuated by said geared ring.
 8. The grinding apparatus as claimed inclaim 1, characterized in that disposed behind the adjustable grindingdisc is a closed space which is connectable to a pressure source for apressure fluid.
 9. The grinding apparatus as claimed in claim 8,characterized in That arranged in a pressure fluid conduit connected tothe space is a pressure controller for determining the magnitude of therelieve pressure acting on the grinding disc.
 10. A grinding apparatuswith grinding discs housed in a casing in which discs at least one isrotatable and which discs between themselves form a grinding space forthe grinding produce consisting of vegetable or similar material, atleast one grinding disc being formed with two concentrical annularelements, characterized in that one of said annular elements isadjustable by means of two screws disposed concentrically relatively oneanother and having threads cooperating with one another, that inaddition the outer screw and a part carrying said annular element havethreads cooperating with one another, that the two pairs of threads arethreaded in the same direction but with different pitches and that oneof the screws is rotationally stationary.
 11. The grinding apparatus asclaimed in claim 10, characterized in that the adjustable annularelement is the radially inner one.
 12. The grinding apparatus as claimedin claim 10, characterized in that a plurality of concentricallydisposed screws are distributed about the circumference of the annularelement and that the outer screw in each pair is adapted to be turned bya common actuating member.
 13. The grinding apparatus as claimed inclaim 12, characterized in that the common actuating member is a gearedring.
 14. The grinding apparatus as claimed in claim 10, characterizedin that the inner screw is devised loosely to bear against the annularelement, but to be locked in relation to said annular element by meansof a locking member located within the inner screw and actuatable fromoutside.
 15. The grinding apparatus as claimed in claim 1, characterizedin that the threads formed between the outer of the two concentricallydisposed screws and the stationary part have a minor pitch than thethreads existing between the screws.
 16. The grinding apparatus asclaimed in claim 1, characterized in that the two pairs of threads areright-threaded.
 17. The grinding apparatus as claimed in claim 12,characterized in that the outer screws in each pair of screws have agearing ring which cooperates with said geared ring and at the same timeis actuated by said geared ring.
 18. The grinding apparatus as claimedin claim 1, characterized in that disposed behind the adjustable annularelement is a closed space which is connectable to a pressure source fora pressure fluid.
 19. The grinding apparatus as claimed in claim 18,characterized in that arranged in a pressure fluid conduit connected tothe space is a pressure controller for determining the magnitude of therelieve pressure acting on the annular element.
 20. A grinding apparatushaving a pair of grinding discs forming between them a grinding spacefor the material to be ground of which discs at least one is rotatable,and at least one of which discs is provided with two concentricalannular elements, characterized in that one of said annular elements isadjustable by screw means including interengaging threads, a closedspace being disposed behind said adjustable annular element, said spacebeing connectable to a pressure source for a pressure fluid, so as torelieve said threads from the grinding pressure between the grindingdiscs during the adjustment of the annular elements.
 21. A grindingapparatus having a pair of grinding discs forming between them agrinding space for the material to be ground of which discs at least oneis rotatable, and at least one of which discs is provided with twoconcentrical annular elements, characterized in that one of said annularelements is adustable by means including two concentrical interengagingscrews, the outer surrounding screw also having threads engaging a screwthreaded part of the casing carrying said annular element, and a closedspace behind said annular element which is adapted to be connected to asource for supplying flUid under pressure whereby to release saidthreads from the grinding pressure between the grinding discs duringadjustment of the annular element.